Mark Zegarelli - SAT Math For Dummies with Online Practice

As you can see from this example, after changing a percentage to a decimal, you can safely drop unnecessary trailing zeros.

For percentages that are less than 10%, introduce one or more place-holding zeros as needed into the decimal that you create. For example:

The absolute value of a number is its non-negative value. For example:

As you can see, when absolute value is applied to a negative number such as –3, the minus sign is dropped. Otherwise, absolute value has no effect on non-negative numbers such as 5 and 0.

When evaluating an absolute value, evaluate the expression inside the absolute value bars, then apply the absolute value, and then evaluate the rest of the expression. For example:

Which of the following is equivalent to ?

(A) –13

(B) –7

(C) 7

(D) 13

To begin, simplify the two expressions inside the absolute value bars:

Next, substitute and :

Now complete the problem:

Therefore, Answer B is correct.

A radical (also called a root ) is the inverse of an exponent — that is, a radical “undoes” an exponent. For example:

so

so

so

The most common type of radical on the SAT is the square root. In this section, I discuss the basics of radicals.

Radicals, such as , arise from reversing the process of squaring a number. That is, they are inverse operations. Table 2-1shows you the results of squaring the first five positive integers and then taking the square root (radical) of the result.

TABLE 2-1Squaring and Taking a Square Root (Radical) Are Inverse Operations

Squares	Square Roots (Radicals)

When you understand how to place radicals such as , , and so forth on the number line, you can see how other values such as , , and so on also fit in. Figure 2-1 shows you a number line that includes specified values of radicals.

FIGURE 2-1:Radicals on the number line.